Attachment anxiety is a form of attachment insecurity characterized by chronic worries about rejection and need for reassurance. Given the critical role a sense of security plays in maintaining healthy relationships, individuals high in attachment anxiety tend to struggle in romantic relationships, which carries serious implications for their broader physical and psychological well-being. Nevertheless, an individual's attachment anxiety continues to change throughout life and can be downregulated by later relationship environments. In this research, we used 7-year longitudinal data (n = 2,057) to examine 1 potential predictor of declines in attachment anxiety in an established romantic relationship: perceiving gratitude from a partner. Random intercept cross-lagged panel analyses supported our prediction that perceiving higher than typical levels of gratitude from a romantic partner was linked with reduced attachment anxiety at that time and, importantly, the following year. These results were independent of the individual's fluctuations in global relationship satisfaction, suggesting the unique power of gratitude. Our findings provide strong evidence that later interpersonal environments can indeed shape an individual's attachment anxiety.